1. Field of the Invention
The present invention relates to a symbol rate testing method. More particularly, the present invention relates to a symbol rate testing method based on signal waveform analysis.
2. Description of Related Art
When designing a communication system (e.g., a WLAN system), the performance of the communication system must be evaluated to ensure that the design of the communication system complies with international standards. During the testing of the system, the symbol rate is one of the most important testing items.
When a designer finishes the design of a communication system, the system must be subjected to a series of tests and verifications to prove that the designed communication system complies with international standards. Among all relevant system testing items, the testing result of the symbol rate of the communication system modules can be used to evaluate the performance of the system.
Several relevant or similar techniques have been disclosed in the conventional art. For example, US Patent Application No. US20030063583A1 discloses a high data rate transmission method and apparatus. According to this application, a high-speed package transmission apparatus for measuring a data transmission rate of a forward link signal at a mobile station is included in a CDMA system, so as to evaluate the system characteristics. However, according to this method, the value of the signal to noise and interference ratio (C/I) of the forward link signal under measurement can only be obtained through complicated statistical function models.
Moreover, US Patent Application No. US20010055334A1 discloses a method and apparatus for determining data rate by detecting variable rate data through hypothesis testing. This application is a vocoder applicable to CDMA having transmitted data frame with a variable rate. During the design of the vocoder, a receiving terminal dynamically measures a signal transmission rate through hypothesis testing. However, the statistical characteristics of the transmitted signal must be determined precisely in advance when measuring the signal transmission rate with this method.
Moreover, U.S. Pat. No. 6,377,618B1 discloses a system and method of data rate detection. This patent uses statistical characteristics of a series of signal sequences transmitted in a setting time to estimate the transmission rate of the transmitted signals. However, for a certain signal interval, this method utilizes calculated auto-correlation functions to find corresponding critical values, so as to estimate the possible signal transmission rate. Therefore, true signal transmission rate cannot be obtained through this technique.
In addition, ROC Patent No. 00418081 discloses a non-invasion blood oxygen concentration meter, and a method of detecting peak and valley of a waveform signal. This patent uses signal levels representing a dynamic peak threshold value and a dynamic valley threshold value to track the peak and valley of the electric signal respectively, and the signal levels can be adjusted dynamically. When calculating the peak and valley, the dynamic peak threshold value and the dynamic valley threshold value are set to be a rising edge of the peak and a falling edge of the valley respectively, so as to find the new rising edge of the peak and falling edge of the valley and the actual peak and valley according to the dynamic searching. Finally, the time that the rising edge of the peak and the falling edge of the valley sustain is counted, and the values and time points of the peak and the valley are confirmed. This method only provides a method of detecting peak and valley, but cannot recognize characteristics of the signal, so is not applicable to the testing of wireless communication products.
As the existing conventional methods cannot provide simple and effective testing, it has become the trend of this field to find a simple method to test the symbol rate.